Well drill



g- 1954 E. A. MORLAN EIAL WELL DRILL Filed Nov. 20, 1951 Ermn A. Moz-Ian Boyd L Scott Henryfl. Woods INVENTORS A T TORNEY Patented Aug. 31, 1954 WELL DRILL Erwin A. Morlan, Floyd L. Scott, and Henry B. Woods, Houston, Tex., assignors to Hughes Tool Company, Houston, Tex., a corporation of Delaware Application November 20, 1951, Serial No. 257,314

11 Claims.

This invention relates to rotary earth boring drill bits and to the rolling cutters therefor, such drill bits being utilized in forming earth bores in the quest for water, oil, gas, sulphur and the like.

The invention is particularly applicable to the conical cutters on earth boring drills wherein two or more such cutters are mounted in juxtaposed relation to roll upon and disintegrate the bottom of the hole. While the invention is hereinafter described in connection with the cone type of well drill, it is to be understood that the invention may find utility in well drills having other types of rolling cutters such as those used in reamers, core bits and cross roller bits.

Much difficulty has been experienced in the drilling of certain earth formations having high compressive strengths ranging from 50,000 to 70,000 pounds per square inch, such as quartzite, chert, granite,etc. which are also extremely hard and abrasive. Frequently only three to five feet of hard, abrasive formation can be cut by a single conventional bit and at a very slow penetration rate. It is then necessary to remove the drill string from the well bore, attach a new hit and go back into the hole. Not only does this require the use of a number of bits for drilling relatively few feet of hole but much time is consumed. When drilling below 12,000 feet, as is frequently the case in modern oil field development, as much as ten hours may be required to come out of the hole, replace the worn drill bit, return to bottom and resume drilling operations. Since operating expense is in the neighborhood of $40.00 per hour or more for rotary drilling rigs capable of sinking a well to these great depths, the cost per foot of penetration is extremely high when said hard formations are encountered.

Also, when conventional rock bits are used to drill formations such as chert, quartzite or the like, care must be taken to withdraw the bit from the hole before the bore of the hole becomes appreciably undersize. It is difficult to ascertain just when the bore hole is becoming undersize. This means that even an experienced driller may pull a bit long before it has become dangerous to continue its use, and he may have the next bit in the hole too long, resulting in an undergage hole. The succeeding bit will be required to ream this undergage hole. This may damage the gage surface so that it may be advisable to ream to bottom with the bit and pull it without making any new hole.

The primary object of the invention is to provide a rotary drill bit capable of drilling hard, abrasive formations at a faster penetration rate 2 and over longer periods of time than had with conventional rock bits.

Another object is to provide a drill bit which will maintain full gage hole in the hardest and most abrasive of rock formations.

Still another object is to provide a drill bit having rolling cutters on which the cutting elements are so formed and arranged that they will dieintegrate full bottom of the hole, are capable of resisting the abrasive action of extremely hard earth formations and will, at the same time, effect rapid disintegration of such formations.

Another object is to provide a composite rolling cutter structure for drill bits in which carbide cutting elements are secured in the body of the cutter in a manner that such material can be utilized without breaking or crumbling under the tremendous impact loads involved in drilling high strength earth formations.

A further object is to provide a drill bit in which the cutting elements on adjacent cutters move in such contiguity that a self-cleaning action is effected.

Still another object is to provide a drill bit having rolling cutters on which the cutting elements are so arranged that they are adapted to interfit and hence to effect the cleaning action already indicated.

Further and more specifically the invention comprehends rolling cutters which comprise a cutter body having wear resistant inserts with their outer ends protruding slightly from the surface thereof and presenting rounded or ovoid surfaces to engage and disintegrate material to be removed by the drilling operation.

It is also an object, in one form of the invention, to provide a rolling cutter comprising a body having peripheral lands thereon, wear resistant inserts being fixed in the lands and having their outer ends protruding from the peripheral surfaces of the lands.

These particular objects, and others, will be attained by the invention as will be more fully apparent from the following description considered in connection with the accompanying drawings in which:

Fig. 1 is an end view showing the cutting surface of a three cone bit embodying the invention;

Fig. 2 is a side elevational view of the bit, a portion of the bit being shown in section rotated into the plane of the paper to more clearly show the illustrated embodiment;

Fig. 3 is an enlarged broken detail showing the age cutting structure;

Fig. 4 is a broken detail showing a slight modification of the gage Cutting structure;

Fig. 5 is a broken detail showing still another form of the gage cutting structure;

Fig. 6 is a perspective view of an alternate form of the wear resistant inserts used in practicing theinvention;

Fig. '7 is an elevational view of a generally cylindrical type of rolling cutter embodying the invention.

The present invention is the result of a discovery that hard formations can be penetrated more rapidly and a single .drillbit will make many more feet of hole than conventional rock bits if wear resistant cutting 'elements of the drill bit having rounded or ovoid surfaces are presented to the formation to effect disintegration thereof. For example 'a'drill bit'embodying the invention was run in West Texas at a depth of approximately 12,000 feet in a formation of abrasive lime and chert stringers. In this formation the drill bit produced 75feet of hole in 23 hours, an average of .327 feetper-houn- In an adjacent well and in the sameformation five'bits of conventional type were used in drilling 78 feet of hole. .These five bits drilled, while. on bottom, at the averagerate of 2.3 feet per hour from which it can be seen that the drill bit of the invention drilled 42 per cent faster than did the conventional bits. However, these five bits required five round trips ofdrill pipe to install the successive new bits..'-.I-Ience, since a round trip at such depth consumes approximately 10 hours, the total'drill rig and crew time for drilling the '78 feet of abrasive lime and chert formation with conventional bits was approximately 84 hours as compared withthebit of the invention which required 33 hours including the round trip for its installation and 23 hours on bottom. It is, therefore, apparent that not only does the drill bit of the invention drillfaster but also a greater footage per bit can be drilled whereby material time is saved and the cost per foot of hole is greatly reduced.

The word -ovoid. is used to state. that the outer .ends of the wear .resistant inserts are rounded or arcuateasdistinguished from conical, pyramidal or chisel edged. Itcomprehends spherical, ellipsoidal or. other rounded .end configuration as-will further appear. Thisfeature of construction serves to .protect the inserts against breakage since the best wear resistant materials, such as carbides, are relatively'brittle. At the same .time, however, it provides adequate coverage of'the bottom of the hole so that uniform disintegration of the bottom is efiected.

An embodiment of the invention, as shown in a three-cone drill bit in Figs. 1 and 2, comprises a head I havinga threaded shank 2 for attachment to the lower end of 'a-drill' string or stem. Downwardly extending legs '3 on the head l'are provided with downwardly and inwardly extending shafts 4, one of which is shown insection in Fig. 2. Cutters '5 enclose-'theinner'ends ofthe shafts S and rotate-upon suitable'bearings-such as the roller bearing *6 at'-the base or heel of the cutter, ball bearings I inwardly therefrom and a friction-bearingfl attheinnermostend of theshaft, as .is .well known inthe .art, the ball bearing 1 serving both toassume radial load and axial thrusts and to retain .the cutter on the shaft.

Each of the cutters 5 'differs'from the others of the set. They are therefore further identified by the numerals [0; II and I2 and are known respectively as the No. 1, N0. 2 and No. 3 cones. This designation is established from the fact that the innermost rows of cutting elements on the cones, beginning with the No. 1 cone, are positioned successively outwardly from the axis of the bit. That is to say the spearpoint 53 on I the cone 10 operates on and proximate the axis spective cutters comprise a body 20 provided with spaced peripheral lands. On cone it these lands are shown, outwardly from the spearpoint l3, at 2 i, 22, and 23. On cone i 4 they are shown at 25 and 28 and on cone l2 they are shown at 2'1, 28 and 29. Each of the lands is provided with a row, or rows, of wear resistant inserts individually identified as 3%. These inserts extend inwardly into the body 28 and are held in place therein with their outer ends protruding from the surface of the associated land. The lands may be of substantially the same width as the transverse dimensions of the inserts 30 but are preferably slightly wider, as shown. Except for the heel lands 23, 26 and. 29, suchlands are so arranged on the respective cones that they are in confrontingrelation with the lands on the adjacent cones. That is to say, each edge portion of a land on one cone .is proximate or overlies anedge portion of aland onan adjacent cone. Hence, the protruding ends of the inserts 3e are so oriented as to adequately cover bottomand the inserts of -a given row have an interfitting relationship with the rows of the adjacent cutters. This not only provides adequate coverage of bottom but also provides efficient utilization of the limited space available for the various portions of the bit and also provides a self-cleaning action of the bit.

Since the inserts contacting the rock support a weight of 40,000 pounds to 50,000 pounds weight or more while drilling with a drill bit 8%" in diameter they must be held .securely in place by some such method as a drive,.press or shrink fit in holes drilled in the lands and hottomed in these holes to support high impact loading. Alternately, the. inserts may be cooled to a relatively low temperature so that contraction thereof will facilitate placement into the holes in the lands, in which case the body 20 may ormay not be heated to further assist in providing the desired fit. The insertsmay also be positioned ina mold so that the metal of .the body 20 and the. lands thereon whencast will bond with the inserts-and provide an integral or unitary structure. Whileparticular-.modes of securing the inserts in'place have been suggested, it is to be understood that the invention is. not confined to any particular method of accomplishing this purpose.

Theuse of ovoid protruding ends on the in serts 35' provides relatively blunt surfaces for engagenient with the surface to be disintegrated. This feature, it would appearwould lead to a slow rate of drilling. Unexpectedly, however, it has been found that the drilling rate in chert and other formations havingsimilar drilla'bility is greatly enhanced over that of conventional bits provided with cutter teethhaving edges'intended to penetrate the formation being drilled. Also, the ovoid protruding ends of the inserts 30are relatively resistant to breakage and for this reason the inserts have a long life since normal wear, as compared with disintegration from breakage, is extremely slow. Furthermore normal wear is of such nature that the ovoid surfaces or ends continue to be ovoid and for this reason cutting effectiveness remains substantially constant over a long drilling period.

Further attention is directed to the spearpoint IS on cone ii), the No. l cone. This spearpoint is preferably made larger than the extension of the balance of the cone to provide an adequate volume of metal to effectively carry a sufficient number of inserts 30 that it will disintegrate the earth formation at the center of the hole and will resist wear as long as other cutting elements on,

the cones.

Severest conditions to be met by the cutting elements of the bit are encountered at and proximate the juncture of the well bottom and the adjacent wall. At the juncture the bottom and the sidewall are mutually self-supporting and for this reason the force applied to effect disintegrating action must be greater than elsewhere on the well bottom. Furthermore, a relatively large volume of formation material must be removed at and adjacent this juncture and, at the same time, gage of the hole must be maintained. To meet these conditions the lands 23, 26 and 29 have rows of wear resistant inserts rolling in the same or substantially the same track on bottom. These portions of the cutters also provide the major portion of traction for the cutters thereby assuring that the cutters will rotate when upon bottom or even when reaming is necessary.

As shown in Fig. 2 the gage inserts may be so oriented that their axes are directed toward the juncture of the wall of the well bore and the bottom thereof. In such case it is preferable that the ovoid ends of the inserts have their surfaces substantially tangent to both the gage surface 3! and the bottom cutting surface of the cutter body. In the preferred structure, and as shown, the axes of the gage inserts are so directed that they substantially bisect the angle formed by the bottom cutting surface of the cutter and the gage surface 3|. Alternately the gage cutting inserts in one or more of the cutters may be positioned slightly outwardly from the position shown in Figs. 1 and 2, as shown in Fig. 3, in which case the outermost surfaces may be flattened at 32 so that a greater area is presented to effect disintegrating action at gage and assure uniform gage.

A still further modification of the gage cutting structure is shown in Fig. 4 wherein the gage inserts are positioned substantially parallel to the gage surface 3| and are substantially flush with such surface. With this gage structure the ovoid projections of the heel inserts cut bottom at the juncture of the bottom of the well bore and the side walls, and the body portions contribute to maintaining uniform gage throughout the useful life of the bit. If desired, the bodies of the inserts may be flattened to provide surfaces 33 for gage cutting surfaces instead of the cylindrical surface indicated at 34.

The modification of the cutting structure shown in Fig. 5 is similar to that of Fig. 4 but the insert 30 is so positioned lengthwise of the cutting surface that the ovoid end 35 serves to maintain gage and the side surface 36 contacts the bottom of the hole to effect disintegrating action thereon.

Fig. 6 shows a modified form of insert that may be used when practicing the invention. In this form the shank 3'! of the insert 30 is noncircular. The outer end of the body is rounded to present an ovoid surface 38 for protrusion from the surface of the cutter body in which the insert is secured to obtain the advantages of the invention. I I

In Fig. 7 the invention is shown as embodied in a generally cylindrical type of cutter 39. The cutter body shown at 20' has annular lands 40 and 4| at its opposite ends and an intermediate spiral land 52. Each land is provided with a series of wear resistant inserts 30 as already explained. It is to be understood that any desired arrangement of the lands and spacing of inserts therein may be used without departing from the spirit of the invention.

Inserts 30 have been referred to as comprising a wear resistant material. Preferably such material is a metal carbide such as chromium, molybdenum, tantalum, titanium, tungsten or vanadium used either as single or multiple car bides. More specifically sintered tungsten car bide inserts have been found to satisfactorily serve the intended purpose. It has also been found that inserts having a transverse dimension of approximately three eights inch and extending into the body 29 a distance approximately equal to such dimension are subject to a minimum of breakage and loss from their locations in the body.

The cutter body 20 is preferably a carburizing grade of steel. However. such material has substantially twice the thermal coefficient of expansion of a metal carbide. This wide disparity of temperature characteristics requires consideration inasmuch as bottom hole temperatures are frequently in excess of 212 Fahrenheit and hence there is a tendency for the inserts 30 to loosen and become displaced from their locations in the body 20. There must be adequate holding power at all times between the metal of the body and the inserts that they will be held in place regardless of temperature and the extreme stresses to which the cutters 5 are subjected. One manner of providing such holding power is to have the inserts 30 larger than the openings 43 to receive them. An interference as great as 0.006 inch may be used. When the insert is forced into the opening 43 there is necessarily an expansive force which causes the interfaces of the body metal and the insert to become conjugate whereby necessary holding power is provided. To facilitate entrance of the inserts into their respective openings each insert is preferably provided with a slight bevel M at its inner end. This feature of construction not only facilitates entrance of the. inserts into their respective openings 43 but also provides a minute space to receive such metal as shears from the wall of the opening 43 as the insert is forced to its terminal position.

While materials and relative dimensions of elements of structures embodying the invention have been mentioned, it is to be understood that such information is intended as illustrative only and does not constitute a limitation of the invention.

The invention claimed is:

1. A rotary well drill comprising, a head, inwardly extending shafts thereon, rolling cutters rotatably mounted on said shafts, at least one of said cutters comprising a body having peripheral lands, and a row of wear resistant inserts in each of said lands, each of said inserts having an ovoid outer end protruding from the periphery of its associated land to present a rounded surface to produce disintegrating action upon the formation being drilled.

2 In, a rotary drill;. bit :comprising: a: head having-inwardly extending shafts :thereonandrolling cutters mounted on; the shafts, the. improvement comprising spaced peripheral lands on each of said cutters, ,and; a, rowo f-. wearresistant inserts in, each of, said; lands, the ends, of said inserts protruding-from the; surface; of the land and said ends. being ovoid topresent: rounded: surfaces to produce disintegrating action upon the formation;being drilled.

3,, In a well drill havingya plurality of rotatable cutters thereon theimprovement comprising, a plurality. of; wearresistant inserts in each cutter, said inserts having ovoid protruding outer ends presenting. arcuate surfaces toiengage and produce disintegratingaction upon the formation being, penetrated by; the drill.

4.,A rolling cutter-for rock drills comprising, abody, andaplurality-of wear resistant inserts insaid-body-end hayingtheir outer ends protrudingfrom thesurface of the body, said protruding, ends being ovoid-so that arcuate surfaces are presentedfor engagement with and disintegrationof materiahtobe, removed by the cutter.

5,. Arolling-cutter for rock drills comprising cuate, surfacesfor. engagement with and disintegration, ofmaterialtobe removed by the cutter.

6.. Ina rolling cutter for drill bits comprising, abody havingabottom, cutting surface and an intersecting gage surface, the improvement com prising a ,row of, wear resistant inserts secured in the body at the intersection of said surfaces, said inserts, extending in.-a direction to approximately bisect the angle, formedby said surfacesand having their outer ends ovoid and,protruding from the surfaceofthe. body whereby the inserts effect cuttingaway of, both the bottom and side wall of a wellbore at. their juncture.

7'. A conical cutter for rotary drill bits comprising, a conical body, a. plurality of cutting elements spaced longitudinally. along the peripheral surface on saidbodma row of. Wear resistant insertssecured insaidbody at the base thereof and in a.d ire ction to approximately bisect the angle formediby the cuttingsurface and the base of the cone, said,inserts having portions protruding from the body to effect disintegration of the earth formationat the juncture, of the bottom and side wall of an earth bore being drilledand to maintain sage of the bore.

8; A roller cone for rock bits comprising a body. cutter elements on said body between the apexand; the. base thereof, a spear point at the apex; of: said'body, anda plurality of wear resistant. inserts: inv said: spearpoint, said inserts having their outer-ends protruding from the surface of thespearpoint and contoured to present arcuate surfacesto engageand effect disinte gration of material to be removed by the spearpoint.

9. A1 rolling cutter for drill bits comprising, a body. there being; a. plurality of circumferentially and axially spaced: cylindrical openings in said body, a'formation disintegrating insert in each of said. openings, each of-said insertshaving a cylindricalportion and an ovoid end portion, the cylindrical1portionyof each-of the inserts having an interference fit in its opening to retain the insert in theopening, the ovoid end of the insert protruding from the surface of the body toeffect formation disintegrating action.

10. In a well-drill having a'plurality of rotatable cutters thereonthe improvement comprising, s-pacedannular landson said, cutters, there being a'plurality of spacedwcylindrical openings in each ofsaid lands, a wear resistant insert in each of saidopenings,,each of said inserts having a cylindrical-portion securing the insert in its associatedopening-byaninterference fit therein, and each of said-'inserts'having anovoid outer'end protruding; from, the surface of the landand presenting an arcuate surface to engage'andproduce disintegrating, action upon the formation being penetratedby the drill.

11. Arollingcutter for rock drills comprising, a body, and-aplurality of wear resistant inserts immovably secured in said body and havingva portionof the surface thereof. protruding beyond the-surface -of the body, said protruding portion beingovoid so-that, each insert presents an.arcuate surface for engagement with and disintegration-of material to be removedby the cutter.

References Cited in the file of this patent UNITED STATES 1 PATENTS Number Name Date 474,297 Hoffmann May 3, 1892 1,010,127 Dingley Nov. 28, 1911 1,502,851 Gale July 29, 1924 1,885,085, Dalzen Oct. 25, 1932 2,117,679 Reed May 17, 1933 2,121,202 Killgore June 21, 1938 2,194,675 Sanders et a1 Mar. 26, 1940 2,234,273 Pennington Mar. 11, 1941 2,244,617 Hannum June 3, 1941 2,626,128 Boice Jan. 20, 1953 

